5-Oxoproline (pyrrolidone carboxylate), a product of the enzymatic degradation of glutathione, mediated by the gamma-glutamyl cycle, is being studied in order to establish its position as a normal intermediate in mammalian metabolism. The concentration of this compound will be determined in tissues and physiological fluids, by the application of a new chromatographic procedure coupled with electron capture detection. Studies are carried out on experimental animals in order to investigate the interrelationship between renal amino acid transport and the formation and excretion of 5-oxoproline. Metabolic inhibitors will be used in experimental animals in order to evaluate the metabolic activity of the gamma-glutamyl cycle in various tissues and its relation to amino acid transport. BIBLIOGRAPHIC REFERENCES: M. Orlowski and S. Wilk: Intermediates of the gamma-Glutamyl Cycle in Mouse Tissues: Influence of Administration of Amino Acids on Pyrrolidone Carboxylate and Gamma-Glutamyl Amino Acids, Europ. J. Biochem. 53, 581-590 (1975); S. Wilk and M. Orlowski: In Vivo Inhibition of gamma-Glutamylcysteine Synthetase by Methionine Sulfoximine: Influence on the Intermediates of the gamma-Glutamyl Cycle, Fed. Proc. 34, 309 (1975).